The invention relates to an ink-jet image recording method using an aqueous ink, in detail, an ink-jet image recording method improved in the glossiness, the friction resistively and the smoothness difference between the image area and the non-image area.
In the ink-jet recording, fine droplets of an ink are flied by various driving principles to record an image and a character. The ink-jet recording method has merits such as that the high speed, low noise and multi-color recording can be easily attained.
The ink-jet recording using a dye ink is spread accompanied with nearing the image quality to that of silver salt photograph and the lowering of the price according to the recent progress of the technology.
The dye is soluble in a solvent, and the dye molecule forms color in a state of a molecular or a cluster. Accordingly, the absorption spectrum is sharp and the color is highly pure and clear since the surroundings of the molecules are similar to each other. The ink-jet image with high transparent feeling and clear hue can be obtained by the dye ink since granular pattern caused by the presence of particles is not formed and scattered or reflected light is not occurred. Moreover, such the ink is excellent in the friction resistivity since no colorant particle is contained in the ink.
On the other hand, the dye ink has a drawback such as that the color light fastness and the resistively against decolorization are low because the reducing of the number of the molecule directly reflects to the color density when the molecule is decomposed by a reaction such as photo reaction. The degradation of the image quality in the course of storage for a long period is large and technology superior to the silver salt photography form the viewpoint of the storage ability of image is not developed yet.
A pigment ink using a pigment having a high light fastness as the colorant is used for the use requiring an image having high resistively against decolorization. However, the pigment ink is inferior in the color reproducibility to the dye ink since the pigment is in a state of pigment particles.
As above-mentioned, the dye ink is superior in the glossiness, transparency and the friction resistively even though inferior in the light fastness, decolorization and spreading resistively, contrary, the pigment ink is superior in the light fastness, decolorization and spreading resistively glossiness even though inferior in the glossiness, transparency and friction resistively.
As the means for solving the above-mentioned problems of the aqueous ink using the water-soluble dye, addition of fine resin particles such as emulsion and latex has been investigated. Japanese Patent Publication Open to Public Inspection, hereinafter referred to as JP O.P.I. Publication, No. 55-18418 describes a proposal relating to a recording medium for ink-jet recording in which latex defined as xe2x80x9ca kind of colloid liquid formed by dispersing a component such as rubber and resin by a emulsifying agent in a state of fine particle in waterxe2x80x9d. As the amount of latex two times or more of the mount of the dye is necessary to improve the light fastness and the spread prevention by the addition of the latex such as that proposed in the publication. Consequently, the stability of the dispersion and the release of the ink are difficultly held and the image equal to that by the silver salt photography in the granularity and the glossiness cannot be obtained yet.
Inks for ink-jet recording containing aqueous dispersion of resin colored by an oil-soluble dye or a hydrophobic dye are proposed for solving the problems of low image density and the low light fastness of the aqueous ink using the water-soluble dye. For example, JP O.P.I. Publication Nos. 55-139471, 58-45272, 3-250069, 8-253720, 8-92513, 8-183920 and 2001-11347 each proposes an ink using emulsion polymerized polymer dyed by the oil-soluble dye or polymer particle in which an oil-soluble dye is dispersed. In such the ink using the colored fine particles, the light fastness improving effect of the ink is reduced and the properties such as the dispersion stability, releasing stability and light fastness are difficultly raised and the image comparable to that of the silver salt photography cannot be obtained when the dye is at the surface or outside of the particle.
JP O.P.I. Publication No. 2001-19880 describes that the density, light fastness and the tone of image can be improved by a chelate dye impregnated colored fine particle. However, such the means is insufficient to obtain an image comparable to that of the silver salt photography. On the other hand, JP O.P.I. Publication No. 2001-139607 proposes a method for improving the blocking of nozzles of the ink-jet head and contact ability by the use of a chelate dye impregnated core/shell type colored fine particle. However, a problem on the storage ability of the ink is remained in this method and the level of light fastness and image quality is not satisfactory for obtaining an image comparable to the image of silver salt photography. Moreover, when such the colored fine particle is used, the colored fine particle is mounted on the surface of the recording medium in the image area so as to form roughed surface. As a result of that the glossiness of the image is reduced.
JP O.P.I. Publication No. 2001-335734 proposes that a colored fine particle having small particle diameter can be obtained by addition of a hydrophobic high-boiling organic solvent additionally to the oil-soluble dye and the resin. However, the glossiness has almost not be improved even when the particle diameter is made small since the particle number should be increased to obtained the necessary image density.
As above-mentioned, the aqueous ink containing the colored fine particle using the oil-soluble dye or the pigment has problems as to the glossiness, friction resistively and smoothness compared with the image formed by the silver salt photography. Therefore, further improvement is required even though such the ink has latent possibility of solving the problems of the usual aqueous ink using the water-soluble dye or the pigment dispersion.
The invention is investigated based on the foregoing problems. The object of the invention is to provide an ink-jet image recording method improved in the glossiness, the friction resistively and the difference of the smoothness between the image area and the non-image area.
The invention and the embodiments thereof are described below.
An ink-jet image recording method using an aqueous ink containing a colorant and a resin and satisfying the following Formula 1;
xe2x80x8315xe2x89xa6wxe2x89xa6150xe2x80x83xe2x80x83Formula 1
wherein, w is a parameter expressed by the following Formula 2;
w=[(dm+ds)/{(NVxc3x97vd)/r3}]xc3x9710,000xe2x80x83xe2x80x83Formula 2
wherein, dm and ds are each a recording density in dpi in the direction of the primary-scanning and the secondary-scanning, respectively, NV is the colored particle content in the ink in weight percent, vd is the radius in meter and r is the radius in meter of the ink droplet; dpi is the number of dot per 25.4 mm.
In the ink-jet image recording method, w is preferably from 20 to 130.
The colorant is preferably an oil-soluble dye in the ink-jet image recording method.
A set of two or more aqueous inks having different colorant density of the same color is preferably employed in the ink-jet image recording method.
A set of two or more aqueous magenta inks having different colorant density and a set of two or more aqueous cyan inks having different colorant density are preferably employed in the ink-jet image recording method.
The set of aqueous inks contains a high colorant density aqueous ink and a low colorant density aqueous ink is preferably employed in the ink-jet image recording method. In this instance the ratio of (colorant density of the low colorant density ink)/(colorant density of high colorant density ink) is preferably from 0.1 to 1.0, more preferably from 0.2 to 0.5, and more preferably 0.25 to 0.4.
The preferable example of the resin is polyvinyl alcohol in the ink.
The volume average radius of the colored particles is preferably from 5 to 100 nm.